Immunoglobulins, Structure, Classification, Functions

Antibody Structure and Types

IMMUNOGLOBULINS

Antibodies are also known by name immunoglobulins. They are glycol-protein in nature which are created by plasma cells. Immunoglobulins act as remark-able part in the feedback of recognizing and binding with specific/particular antigens for example Viruses, bacteria etc. Antigens are foreign particles. When they come from outside they are not anymore part of human body so they become foreign particles and invade to enter in our body and blood, against these antigens our immune system activates and make antibodies by reacting with them. When we get infection or immunization, in the serum amount of antibodies get elevate, the raised level of antibody is known as the immune serum.

Structure of Antibodies:

Human antibodies (Immunoglobulins) are glycol-proteins in nature and each molecular consist of two set/pair of non-identical sizes of poly-peptide chains. The small chains of immunoglobulins is known as light   (L) chains and the heavy/large one is called as (H) chains. These small (L) and heavy/large (H) chain are link to-gather by a bond name as di-sulphide bond. The small (L) chain is about 25,000 in molecular weight and the heavy/large (H) chain is about 50,000 in molecular weight. Heavy/large (H) chains makeup and antigenically or chemically differ from each class/category and can be identify by a Greek symbol and have a close similarity to immunoglobulin (Antibodies) are following:

Antibody Structure

Antibodies Classification (H-Chain):

IgM Mu (μ)
IgG Gamma  (γ)
IgA Alpha  (α)
IgD Delta  (δ)
IgE Epsilon  (ε)
Types of Antibodies

The heavy (H) chains having a resemblance in all antibodies types. There are two class of: Kappa (κ) Lambda (λ) .The antigen union area of the molecule/particle is found at amino-terminals. This amino-terminal have both light (L) and Heavy (H) chains. The sequence of amino acid of the carboxy-terminal 50 % occurs in a constant or continual sequence and is therefore called as the constant region, while on the other hand the amino acid sequence in the amino terminal 50% of the chain is highly variable or changeable and is that’s why called as the variable region. The immunoglobulin specificity/particularity range is depends on the variability or discrepancy of amino acid sequences in the variable region of heavy (H) Chain.

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Characteristics and Function of Antibodies:

IgG

  • By fore this class is chief of all immunoglobulin in human blood and it covers about 80 % of the total amount of antibodies and is equally circulate between extra-cellular as well as in intra- cellular compartments.
  • These immunoglobulins contain small amount of carbo-hydrates as compared them to others ones. They have about 23 days of life span.
  • This is the only antibodies which cross the placenta of the fetus mother. They play vital role in passive immunity. It help in phagocytosis process by binding with micro-organism like bacteria etc.
  • It help against those micro-organism or infectious agents which are active in the blood or tissues.
  • If we give IgG passively it will suppresses or terminate homologous synthesis of antibodies by mechanism known as Icedback.
  • During the delivery of child birth, this IgG is used in Iso-immunization for women and administrated of Anti (Rh) and D-IgG. There are 4 sub-types of IgG which are: IgG, IgG-2, IgG-3, and IgG-4.

IgA

  • IgA is 2nd large class, compose of 10 to 13% of blood antibodies and have 6 to 8 days of lifespan. IgA is major antibodies and present in saliva, tears and colostrum.
  • IgA play vital role in Lovac-immunity and against pathogens present in gut. It act as reducing agents. This antibody can resist to some digestive enzymes.
  • Those organism who bind or attach with mucosal cells surface, IgA inhibit them by covering them and prevent their adhesion mechanism.
  • IgA also play role in the process of phagocytosis and killing of the intracellular organisms.
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IgM

  • This antibody compose of about 5 to 8% blood immunoglobulins and about 5 days of lifespan.
  • IgM synthesis get started in fetus from the age of 20 weeks.
  • If the IgM is present in the blood of fetus it means that fetus having an intra-uterine infection and its diagnosis is so important for congenital infections for example HIV, Rubella, Toxoplasmosis and Syphilis.
  • If deficiency of IgM take place it will clearly indicate that patients is suffering with septicemia.
  • IgM cannot cross the placenta of the fetus mother.

IgD

  • IgD is very similar according to its structure. It has lifespan around 3 days.
  • IgD with the help of IgM aid in recognition receptors for antigen and present on the surface of non- stimulated B-lymphocytes.
  • This antibody is abundant in extra-vascular and cannot cross the placenta.
  • When the patients get asthma or eczema infection the IgD level will raise in the serum.

IgE

  • T airways and intestinal tract lining synthesize the IgE immunoglobulins.
  • IgE produce whenever person get worm infection and also play vital role in hypersensitivity because of its anaphylactic nature.
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